Helicopter



FIG. 1 is a top view of a helicopter;

FIG. 2 is a bottom view of the helicopter;

FIG. 3 is a front view of the helicopter;

FIG. 4 is a rear view of the helicopter;

FIG. 5 is a side view of the helicopter; and,

FIG. 6 is an opposite side view of the helicopter. 

The ornamental design for a helicopter, as shown and described. 